The effect of spontaneous breathing on systemic interleukin-6 during ventilator weaning

During the weaning process, spontaneous breathing trials (SBTs) involve cardiopulmonary stress for ventilated patients. As interleukin (IL)-6 is a major modulator of the stress response, we hypothesised that systemic IL-6 increases during a SBT and that this increase is more evident in SBT failure. 49 SBTs of 30-min duration were performed on different mechanically ventilated patients, and classified as SBT failure or success. Blood samples were drawn before and at the end of the SBT. An additional sample was drawn 24 h later in a subset of patients (n = 39). Serum IL-6 levels and other inflammatory mediators commonly associated with stress were determined. IL-6 levels increased from mechanical ventilation to spontaneous breathing in all patients (p = 0.02) and in the chronic obstructive pulmonary disease (COPD) population (p = 0.05) with SBT failure compared with success, but not in non-COPD patients (p = 0.12). After 24 h of SBT stress, IL-6 levels decreased in patients with SBT failure (under mechanical ventilation at that point) (p = 0.02) and those with weaning success (p = 0.04). No changes were observed in the remaining inflammatory mediators. Systemic IL-6 increases during a 30-min, failed SBT, especially in COPD patients. Future studies may corroborate the different IL-6 responses among different populations who initiate weaning, together with the potential clinical implications.